Bacillus thuringiensis has been known for years for coding for δ-endotoxin crystal proteins. A large variety of endotoxins have been described and characterized, many of them having reported insecticidal activities. Most of these have molecular weights in the range of 130-140 kDa and 65-80 kDa (Schnepf et al., 1998). Recently, a novel endotoxin protein has been identified and designated Cry31Aa1 (also called parasporin) (Mizuki et al., 2000). It is an 81 KDa protein encoded by a 2169 bp gene that has been characterized as having a selective activity as a human Leukemic Cell-Recognizing Protein (Mizuki et al., (1999) and (2000)). No other member of this novel family of endotoxin has yet been reported.
It is therefore an object of the present invention to provide a new bacillus thuringiensis strain expressing a new member of this novel family of δ-endoxins displaying advantageous cytotoxicity against human cancer cells.